1. Field of the Invention
The present invention relates to an electric motor car control apparatus.
2. Description of the Related Art
According to general techniques of electric double layer capacitor series connection in railway vehicles, as disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-18702 and “A Study for Electric Double Layer Capacitor Series Connection for Railway Contraction”, 2003 JIASC Conference 3-32, so-called regeneration limiter control is performed in a technique using a VVVF inverter. Regeneration limiter control is performed as follows. When a VVVF inverter is set, during regeneration braking, in a light-load regeneration state in which a load which absorbs regeneration energy on the overhead wire side becomes insufficient, a rise in overhead wire voltage due to a rise in the capacitor voltage of the VVVF inverter is detected, and the rise in overhead wire voltage is suppressed by reducing the regeneration braking force in accordance with the capacitor voltage. In this case, when the regeneration braking force is reduced, the reduced braking force is compensated for by the force generated by a mechanical brake. A DC/DC converter which performs charging control on a power storage device detects a light-load regeneration state upon a rise in the capacitor voltage of the DC/DC converter during braking, and controls a charging current to the power storage device so as to suppress a rise in capacitor voltage. The amount of power absorbed in the power storage device by the DC/DC converter and the regeneration braking force reduction control amount by VVVF regeneration limiter control are based on the respective filter capacitor voltages. In addition, control is performed to make an input current to the VVVF invert equal to an input current to the DC/DC converter. Alternatively, control is performed to make an input current to the overhead wire zero.
According to the above technique, the DC/DC converter detects a light-load regeneration state upon a rise in the capacitor voltage of the DC/DC converter during braking, and controls a charging current to the power storage device so as to suppress a rise in capacitor voltage. At this time, the amount of power absorbed in the power storage device by the DC/DC converter and the regeneration braking force reduction control amount by VVVF regeneration limiter control are determined by the respective filter capacitor voltages without direct control of them. For this reason, absorbed energy becomes insufficient or excessive with respect to energy corresponding to a regeneration load shortage due to capacitor voltage detection errors and voltage differences, resulting in failure to effectively absorb energy.
Although control is performed to make an input current with a VVVF equal to an input current to the DC/DC converter or control is performed to make an input current to the overhead wire zero, it is difficult in this method to discriminate a load state on the overhead wire side, and regeneration energy which can be returned to the overhead wire side may be absorbed by the power storage device through the DC/DC converter.
If absorbed energy is insufficient relative to energy corresponding to a regeneration load shortage, the overhead wire voltage rises, and VVVF regeneration limiter control operates to reduce the regeneration braking force. As a result, compensation by the mechanical brake is executed. In contrast to this, when absorbed energy becomes excessive, energy that can be returned to the overhead wire side is absorbed by the power storage device. Since the absorption capacity of the power storage device is limited, absorption cannot be continued.
In either of the above cases, the capacity of the VVVF power storage device cannot be used fully. That is, absorption cannot be effectively performed.